Westerhoff Paul, James Jennifer
Department of Civil and Environmental Engineering, Arizona State University, P.O. Box 5306, Tempe 85287-5306, USA.
Water Res. 2003 Apr;37(8):1818-30. doi: 10.1016/S0043-1354(02)00539-0.
Nitrate removal by laboratory and field continuous-flow zero-valent iron (Fe(0)) packed bed columns was evaluated for different influent water qualities (pH, dissolved oxygen (DO), nitrate concentration) and several months of operation (600-1500 bed volumes (BVs)). In contrast to previous batch experiments with Fe(0) where nitrate was stoichiometrically converted to ammonium, only 70% of the applied nitrogen was recovered as nitrate, ammonium, or nitrite (<0.1mg/L) during shorter-term column tests (2-20 BVs) and less than 25% of the applied nitrogen was recovered during longer-term field testing (500-1000 BVs) at elevated nitrate levels (approximately 25mg N/L). Nitrate removal was accompanied by a pH increase, DO decrease, and soluble iron increase. During longer-term operation (500-1500 BVs) iron and calcium precipitates were observed, by SEM and EDX analyses, to form in the packed columns. Precipitation led to cementation and reduction in permeability for the Fe(0)/sand media in the packed column. Different abiotic and microbial-mediated mechanisms may be involved during shorter- and longer-term operation of Fe(0) systems and the role of iron precipitates should be further evaluated.
针对不同进水水质（pH值、溶解氧（DO）、硝酸盐浓度）以及数月的运行时间（600 - 1500床体积（BV）），对实验室和现场连续流零价铁（Fe(0)）填充床柱去除硝酸盐的情况进行了评估。与之前使用Fe(0)的批次实验不同，在之前的实验中硝酸盐按化学计量转化为铵，而在短期柱试验（2 - 20 BV）期间，仅70%的施加氮以硝酸盐、铵或亚硝酸盐（<0.1mg/L）的形式回收，在较高硝酸盐水平（约25mg N/L）下进行的长期现场试验（500 - 1000 BV）期间，回收的施加氮不到25%。硝酸盐去除伴随着pH值升高、DO降低和可溶性铁增加。在长期运行（500 - 1500 BV）期间，通过扫描电子显微镜（SEM）和能量散射X射线光谱（EDX）分析观察到填充柱中形成了铁和钙沉淀物。沉淀导致填充柱中Fe(0)/砂介质的胶结和渗透率降低。在Fe(0)系统的短期和长期运行过程中可能涉及不同的非生物和微生物介导机制，铁沉淀物的作用应进一步评估。
